Variable Second Pad Keel

ABSTRACT

By including a Variable Second Pad Keel, a watercraft experiences a reduction in Slamming forces as well as generally improved Seakeeping and Seakindliness.

RELATED APPLICATIONS

This continuation-in-part application claims the benefit of U.S.Non-Provisional application Ser. No. 14/599,164 filed Jan. 16, 2015, thedisclosures of which are herein incorporated by reference.

TECHNICAL FIELD

The field discussed herein relates generally to watercraft hullconfiguration.

BACKGROUND

It is well known that flat, zero-Deadrise hull surfaces have the highestplaning efficiencies, and many prior art watercraft incorporate flatsections to hull bottoms to improve total hull planing efficiency.Planing efficiency refers to efficiency of energy use while underway; ahull having high planing efficiency can use less fuel and produce lesswake than a hull having low planing efficiency. However, it is also wellknown that wide, flat planing surfaces generate strong impacts to thehull (and watercraft occupants) when such a planing surface re-contactsthe water surface after separating from the water surface, for instancewhen planing through choppy conditions and when re-contacting the watersurface after the watercraft launches off wave crests. These strongimpacts are called “watercraft slamming”. To minimize slammingassociated with flat planing hulls, prior art watercraft have limitedthe flat hull areas to selective portions of the hull. Typically, theflat hull areas employed by prior art watercraft have been relativelyshort, narrow, wedge or delta-shaped areas of the hull keel that arewidest at the transom, taper in width forward from the transom, andblend into V-shaped sections in the hull's forebody.

Some prior art watercraft designs employ truncated, or “padded”,V-shaped hull structures wherein the bottom of a V-shaped hull has beencut away (“truncated”) to create a flat “pad” area integral to thehull's bottom. Other prior art watercraft have employed distinctly “flatpad keels” wherein the flat pad projects below the theoreticalconvergence of the sides of a watercraft's V-shaped hull. It is wellknown that truncated V-shaped hulls and pad keels can cause maneuveringand turning problems such as side slip and lack of directionality. As aresult, prior art watercraft with flat hull portions frequently addedstrakes, reverse strakes, sponsons or other structures to the hull toincrease hull grip.

FIG. 0A shows a relationship between lift fraction of flat plate andDeadrise, but does not explain the relationship of slamming force tothose variables. As shown by FIG. 0A, the 0 Deadrise of a pad keelprovides significantly more lift, about 33% more than a 20 degreeDeadrise V-shaped hull, if the Pad Keel Sides have Deadrise of 45degrees or greater, the peak slamming pressure as the hull is immersedwill be no greater than the initial entry pressure. There is unmetdemand for a hull design with >45 Deadrise Pad Keel Sides with improvedSeakindliness, Seakeeping, substantially reduced Slamming, with lessviscous drag and minimal reduction in Planing Efficiency and withAcceptable Slamming Force. Therefore, the technical problem to be solvedis to design a Hull that combines a large Pad Keel with Pad Keel Sideswhose Deadrise of 45 degrees or greater create a Hull with improvedSeakindliness, Seakeeping, substantially reduced Slamming, with minimalreduction in Planing Efficiency, compared to prior art deep V-hulls andPlaning Hulls.

The foregoing examples of the related art and limitations relatedtherewith are intended to be illustrative and not exclusive. Otherlimitations of the related art will become apparent upon a reading ofthe specification and a study of the drawings.

SUMMARY

The following examples and aspects thereof are described and illustratedin conjunction with systems, tools, and methods that are meant to beexemplary and illustrative, not limiting in scope. In various examples,one or more of the above-described problems have been reduced oreliminated, while other examples are directed to other improvements.

As discussed herein, watercraft can benefit from Hull designs utilizinga Second Pad Keel of varying width, surface shape, and Taper. Such Hulldesigns can include a Self-Flooding and Self-Bailing Pad Keel Plenumequipped with a Bow Pocket Vent.

As shown by FIG. 0A, the 0 Deadrise of a pad keel provides significantlymore lift, about 33% more than a 20 degree Deadrise V-shaped hull.Therefore, this allows the Pad Keel Sides to be designed to mitigateslamming rather than generating lift. FIG. 0B shows the effects ofDeadrise and the relationship between pressure forces of wedge sections(e.g. a V-shaped hull) from initial entry through increasing immersion.As shown in FIG. 0B, if the Pad Keel Sides have Deadrise of 45 degreesor greater, the peak slamming pressure as the hull is immersed will beno greater than the initial entry pressure, which translates to acompression force if the hydrodynamics of the hull are analogized to anautomotive shock absorber.

Advantageously, Hull designs benefiting, from these advancementsoutperform those having merely flat surfaces, V-shaped, previous PadKeel, hulls. Hull designs including advancements disclosed herein enjoyhigh Planing, efficiency without high Slamming, and exhibit excellentSeakindliness and Seakeeping. By analogy, the hydrodynamic properties ofa Second Pad Keel allow it to function on a watercraft like anautomotive strut or shock absorber functions on a car. This improves theexperience of operating the watercraft in the way that an automotiveshock absorber improves the experience of driving a car.

Herein as described are Hull configurations employing a Second Pad Keelof varying width, surface shape. Taper, and Deadrise (depending on thepurpose of the craft). Embodiments of the Hull can include a Pad KeelPlenum that Self-Floods and Self-Bails via a Bow Pocket Vent on the PadKeel Sides. Advantageously, this provides a novel watercraft made withthe Hull that has improved Seakeeping, Seakindliness, payload, andPlaning efficiency, and reduced Slamming compared with prior art Planinghulls and V-Hulls. This is achieved by combining the efficiency benefitsof a wider and/or multiple Pad Keels without having negative Seakeepingor handling problems associated with a Deep-V The Hull. The Hull of theinvention can be retrofitted to existing watercraft and can be employedin new watercraft designs.

The Self-Flooding and Self-Bailing Pad Keel embodiments of the inventiondynamically improve Seakeeping and Seakindliness over a range of speeds.A Bow Pocket Vent provides atmospheric air ingress to the interior of aHollow Plenum and allows the Plenum to Self-Flood and Self-Bail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 0A is a graph of the relationship between lift fraction of flatplate versus its Deadrise. FIG. 0B is a graph of the relationshipbetween pressure and Deadrise of a wedge upon water entry

FIGS. 1A-1H and 1J depict a typical deep-V watercraft with a ConcentricPad Keel that can be attached (in FIG. 1A) or is attached (in FIGS.1B-1J) to the bottom of the Hull of the typical deep-V watercraft. Thereis no FIG. 11 (1-“eye”).

FIGS. 2A-2C generally depict the water flow present during the impact ofa Second Pad Keel and the water as well as the forces present during animpact of a V-Hull and the water.

FIGS. 3A-H and 3J depict a Uniform Second Pad Keel. There is no FIG. 3I(3-“eye”).

FIGS. 4A-C depict a Truncated, Ventilating Second Pad Keel.

FIGS. 5A-C depict a Truncated, Aft Rocketed Second Pad Keel.

FIGS. 6A-C depict an Aft Expanding Second Pad Keel.

FIGS. 7A-C depict an Aft Expanding and Rockered Second Pad Keel.

FIGS. 8A-C depict an Aft Rockered Second Pad Keel.

FIGS. 9A-C depict an Aft Expanding, Truncated and Ventilating Second PadKeel.

FIGS. 10A-C depict an Aft Expanding, Truncated and Aft Rocketed SecondPad Keel.

FIGS. 11A-C depict an Aft Expanding, Truncated and Rockered Second PadKeel.

DETAILED DESCRIPTION

In the following description, details are presented to provide athorough understanding of the invention. One skilled in the relevant artwill recognize, however, that the concepts and techniques disclosedherein can be practiced without one or more of the specific details, orin combination with other components, etc. In other instances,well-known implementations or operations are not shown or described indetail to avoid obscuring aspects of various examples disclosed herein.

“−6 to +6 Deadrise” means Deadrise of −6 Degrees to +6 Degrees and isotherwise known as “Flat” (in the case of +/−1 Degree Deadrise). “FlatDeadrise” have −6 to +6 Average Deadrise.

“6-19 Deadrise” means Deadrise greater than 6 degrees but less than 20degrees and is known as “Low Deadrise”.

“20-45 Deadrise” means Deadrise greater than or equal to 20 degrees butless than 45 Degrees and is otherwise known as “High Deadrise”.

“>45” Deadrise means Deadrise of 45 to 90 Degrees and is otherwise knownas “Ultra High Deadrise”.

“Above” means higher in elevation when viewed from the Bow or Transom.

“Acceptable Slamming Force” is a qualitative measure of the degree ofSlamming that persons on a watercraft will experience, without feeling,extreme discomfort. Acceptable Slamming Force is a personal variable andis very dependent upon the rate of deceleration during a Slam.

“Aft End” means, with respect to a Second Pad Keel, an end of the SecondPad Keel, at a point along the Centerline of the watercraft, at of theForward End of the Second Pad Keel.

“Angle of Attack” means the angle that the line between fore and ofpoints on a Hull, or a longitudinal part of a Hull, make with theincoming flow.

“Beam” is the width of a watercraft.

“Below” means lower in elevation when viewed from the Bow or Transom.

“Blend” means, with respect to portions of a hull, to join two or morepanels continuously so as to provide a smooth surface at theirintersection(s).

“Bow” means the forward part of a watercraft.

“Bow Pocket Vent” means an opening at the Bow on a Pad Keel Side with aSpray Deflector that provides a channel between the surface of the PadKeel and the internal cavity of a Hollow Plenum Pad Keel.

“Chine” means the edge formed on the Hull of a flat bottomed orV-bottomed watercraft where the Hull bottom joins the Hull sides,

“Concentric Pad Keel” means a Hull structure comprised of concentric andsymmetric Flat Pad Keels with the larger or Main Pad Keel Above thesmaller or Second Pad Keel. The Main Pad Keel is connected and dependsbelow the rest of a watercraft Hull on Ultra High Deadrise Main Pad KeelSides. The Second Pad Keel is connected and depends below the Main PadKeel on Ultra High Deadrise Second Pad Keel Sides. There may beadditional Pad Keels Above the Main Pad Keel Sides.

“Deadrise,” means (in a Transom or Bow view of the Hull) the angle of asection of a Hull relative to the water when the watercraft is notheeled over, i.e. when the watercraft is upright, e.g., “Low Deadrise,”“High Deadrise,” and “Ultra High” Deadrise.

“Deep-V Hull” means a Hull with High Deadrise at the Transom whenmeasured from the centerline of the Transom to the outboard edge of theChine.

“Design Waterline Beam” means the width of a watercraft as measured inthe Y dimension at the watercraft's waterline when the watercraft isloaded to its design condition.

“Design Waterline Length” means the length of a watercraft as measuredin the X dimension at the watercraft's waterline when the watercraft isloaded to its design condition.

“Disturbed Water Surface” means the waves or ripples caused on the watersurface from a Hull entering the water.

“Expand,” “Expands,” or “Expanding” means, with reference to the SecondPad Keel, that the Width of the Second Pad Keel Sides at the connectionwith the Main Pad Keel increases Fore to Aft and blends to the width ofthe Main Pad Keel at the Transom or within half the distance between theLongitudinal Center of Buoyancy and the Transom.

“Fine Entry,” or “Fine Entry Bow” means the shape of the Bow that isdesigned to slice or cleave through waves. A typical Fine Entry Bow hasa Forefoot Deadrise greater than 45 degrees.

“Forebody” means the part of the watercraft forward of the Midship.

“Forefoot” means the part of the Keel which curves and rises to meet theStem.

“Forward End” means, with respect to a Second Pad Keel, a region of theSecond Pad Keel, forward of Midship along the Centerline of thewatercraft.

“Forward Apex” means, with respect to a Second Pad Keel, a forward mostpoint of the Second Pad Keel.

“grips” as used generically with a lowercase “g” means latitudinalpressure exerted against water by longitudinal features of a watercrafthull. Grip is useful in controlling the direction of the watercraft,particularly at high speeds. Am example of usage: “Although traveling atspeeds in excess of 50 knots, the watercraft's Hull had good grip anddid not spin out during turns.”

“Height” means a measurement of a watercraft, a watercraft structuralelement, or a watercraft feature in the Z Dimension.

“Hollow Plenum” means the internal cavity formed by the Pad Keel, PadKeel Sides and an air and watertight top cover joining to both Pad KeelSides and the adjacent Hull Panel(s) Above it. It functions to conductair or water to openings in the Pad Keel or Pad Keel Sides to Self-Bailor Self-Flood the cavity. A Bow Pocket Vent provides an access foratmospheric air entry when the Plenum is Self-Bailing or to allow air tovent out of the Plenum when the Plenum is Self-Flooding.

“hull” (in lower case letters) means the body of a prior art watercraftbetween the deck (which may be the inner surface of the hull) and thekeel. The hull is the shaped structure of the bottom of a watercraftthat provides buoyancy and seaworthiness. “Hull”, with an initialcapital H, means the Hull of an embodiment of the invention describedand claimed herein.

“Hull Chine Beam” means the width of as watercraft as measured betweenits port and starboard Chines.

“Hull Modification” means any change or alternation made to a Hull thatdiffers from its original design.

“Heel,” “Heeled,” or “Heeling” refer to a watercraft that is leaningeither to starboard or to port.

“Immersed Area” or “Wetted Surface Area” means the wetted portion of aHull and appendages at and below the waterline.

“Initial Slam” means the initial impact of a Hull on a water surfaceduring Re-entry e.g. by impacting a wave or the ocean surface while awatercraft is underway.

“Inwardly-Stepped” means a series of transverse (Y Dimension)discontinuities in the direction of the centerline in a panel or panelsof a watercraft's hull.

“Keel,” means the structure of a watercraft hull that extendslongitudinally along the center of its bottom and that often projectsfrom the bottom. See also, “Pad Keel” and “Pad Keel Sides”.

“Length” is synonymous with Design Waterline Length and is a measurementin the X Dimension.

“Length To Beam Ratio” is the ratio of Design Waterline Length to DesignWaterline Beam For example, a Hull with a Design Waterline Length of 30and a Design Waterline Bean of 5 will have a Length To Beam Ratio of 6.

“Longitudinal Center of Buoyancy” means the point on the Keel, along theCenterline, in the X dimension, at which the watercraft balances withrespect to Buoyancy.

“Longitudinal Step” means a fore and aft vertical discontinuity on theHull bottom surface and appears as a step when viewed in Transom or Bowviews.

“Main Pad Keel” or “MPK” means the Pad Keel in a Variable Second PadKeel configuration Above the Second Pad Keel.

“Main Pad Keel Sides” means the Ultra High Deadrise Hull Panels thatconnect the Main Pad Keel and depend from the remainder of the HullAbove it.

“Midship” means the location on a watercraft that is approximatelyequally distant from Bow and stern, e.g. a location between 40% and 60%of the length from Bow to stem.

“Outboard” means in a position that is away from the center line of thehull of a watercraft.

“Pad Keel” means the flat Hull surface that protects below thetheoretical convergence of the sides of the watercraft's V-shaped Hull,Pad Keels increase hydrodynamic lift compared to traditional keels whena watercraft is underway.

“Pad Keel Sides” means the Ultra High Deadrise Hull Panels that connecta Pad Keel to, and depend from, the remainder of the Hull Above it.

“Pad Keel Side Ventilator” means a Pad Keel Side Hull Panel that isInwardly-Stepped towards the centerline from the Pad Keel Sides, tapersat its aft end to blend with the Pad Keel Sides, and has one or moreopenings at its forward end, through which air and water can Self-Bailand Self-Flood the Hollow Plenum and provide air ventilation to thePanels aft of it when the craft is underway.

“Panel” means a plating component of a Hull. A combination of Panels andother components of a Hull form the Hull itself.

“Planing” means riding on the surface of water as in “hydroplaning” or“aquaplaning,” where lift is provided by hydrodynamic pressure.

“Planing Hull” means a Hull shape that allows at least part of its Keelto rise above the water's free surface, and to ride up on the after partof the Hull, allowing the watercraft to move much faster with some ofthe watercraft on the surface of the water.

“Planing Surface” or “Planing Surfaces” mean a section, or sections, ofa Hull having Flat Deadrise that operate to ride at least partially onthe surface of water when a watercraft is underway.

“Plenum” is a synonym of “Hollow Plenum”.

“Re-entry” means the reentry of a watercraft hull into a water surfaceafter all or part of the hull has left the water's surface, typicallywhen the watercraft is underway, e.g., through choppy water or has beenlaunched off a wave crest.

“Rocker” or “Rockered” means, with reference to the Second Pad Keel,that the Height of the Second Pad Keel Tapers in the Z dimension at itsAft End to a point forward of the Transom.

“Rough”, “Rough Water”, or “Rough Seas” are synonyms that mean wind andwave conditions that cause uncomfortable watercraft motions.

“Seakeeping” or “Seakeeping ability” are synonyms for the qualitativemeasure of a watercraft's ability to maintain functionality in RoughWater.

“Seakindly” or “Seakindliness” are synonyms for the qualitative measureof a watercraft's ability to maintain occupant comfort in Rough Water.

“Second Pad Keel” or “SPK” means the Pad Keel Below the Main Pad Keel ona Hull narrower than the Main Pad Keel.

“Second Pad Keel Sides” means the Ultra High Deadrise Hull Panels thatconnect the Second Pad Keel to, and depend from, the Main Pad Keel.

“Self-Bailing” or “Self-Bail” means a feature of a watercraft thatdrains water by air pressure or gravity, e.g. through an opening or bypressure gradient.

“Self-Flooding” or “Self-Flood” means a feature of a watercraft thatallows water to enter and flood an internal Plenum automatically, e.g.by water pressure alone.

“Slam” or “Slamming” means to crash down hard on a water surface,referring to the action of a watercraft.

“Spray Deflector” means a covering on a Bow Pocket Vent that preventsincoming spray from entering the opening.

“Stem” means the forward most part of the Bow.

“Taper” means a change in Width, or Height over the Length.

“Transom” means the flat surface forming the stern of a watercraft.

“Transverse” means in the direction of port to starboard or vice versa.

“Transverse Step” means a port to starboard (athwartship) verticaldiscontinuity to a watercraft's Hull and it appears as a step in theHull bottom in a side view.

“Transversely Stepped” means a Hull including a single or multipleTransverse Steps.

“Truncated” means, with reference to a Second Pad Keel, in the XDimension, that the Second Pad Keel terminates at a location forward ofthe Transom, aft of which, a Main Pad Keel continues.

“Ultra High Deadrise” or “UHD” refers to a Hull, or portion of a Hull,that is sharply V-shaped and has Deadrise of between 45 and 90 degrees.

“Undisturbed Water Surface” means the surface of water yet to be enteredby the Hull.

“Uniform” means, with reference to the Second Pad Keel, that the SecondPad Keel runs the length of the Main Pad Keel from Transom to ForwardApex, is neither Expanding nor Rockered, and Tapers Vertically at theForward End to ½′ or less at the Forward Apex.

“Un-Wet” means in reduced contact with water through aeration.

“Variable Second Pad Keel” means a Hull structure comprised of symmetricFlat Pad Keels with the larger or Main Pad Keel Above the smaller orSecond Pad Keel. The Second Pad Keel is connected to, and depends Below,the Main Pad Keel on Ultra High Deadrise Second Pad Keel Sides. AVariable Second Pad Keel differs from a Concentric Pad Keel in that ithas a Taper through either an Expanding and/or Rockered Second Pad Keel.

“Ventilate” or “Ventilating” means to conduct atmospheric air outboardthrough submerged Hull openings to partially un-wet submerged Hullsurfaces using a negative pressure gradient caused by the Venturi effectwhile the craft is underway. The un-wetting of submerged Hull surfacesreduces the Hull's Viscous Drag.

“Ventilating Air” means atmospheric air used to Ventilate the Hull.

“V-Hull” means a Hull composed of two distinct planar surfaces thatintersect at the Keel at a Deadrise. A V-Hull is so-named because itresembles the shape of the letter “V” in Bow view.

“Viscous Drag” is friction force acting, opposite to the relative motionof a watercraft moving through a fluid.

“Water Entry Deceleration” means, with reference to a Hull enteringwater, or a portion of a Hull entering water, the deceleration of a Hullas the Hull enters the water.

“Watercraft Re-Entry Initial Deceleration” means, with reference to aHull Re-entering water, or a portion of a Hull Re-entering water, thedeceleration of a Hull as the Second Pad Keel Re-enters the water.

“Watercraft Re-Entry Vertical Deceleration” means with reference to aHull Re-entering water, or a portion of a Hull Re-entering water, thedecrease in vertical velocity of the Hull as the Hull Re-enters thewater.

“Waterline” means the level normally reached by the water on the side ofa watercraft.

“Wedge Ventilator” means a wedge shaped Hull Panel that projectsdownward at its aft end from a Longitudinal Step, tapers at its forwardend to blend with the Longitudinal Step, and has one or more openings atits aft end, through which air and water can Self-Bail and Self-Floodthe Hollow Plenum and provide air ventilation to the Panels aft of itwhen the craft is underway.

“Width” defines a measurement in the Y Dimension.

“X Dimension” defines a measurement along the line from bow to stern,otherwise known as Length.

“Y Dimension” defines a measurement along the line from port tostarboard, otherwise known as Width.

“Z Dimension” defines a measurement along the line from deck to keel,otherwise known as Height.

A watercraft's Planing performance efficiency is improved and areduction in Slamming Forces is realized by having a Variable Second PadKeel structure configuration. A watercraft designed with a VariableSecond Pad Keel in accordance with the teachings provided herein has aFlat Main Pad Keel projecting, downward on Main Pad Keel Sides from atypically V-shaped watercraft Hull. The Main Pad Keel has Main Pad KeelSides with Deadrise between 45 degrees to 90 degrees. The height of theMain Pad Keel sides at the Transom is 20% to 30% of the Main Pad Keelwidth at the Transom. The Main Pad Keel is wiriest at the Transom andits width Tapers towards the Bow. A Second Pad Keel, smaller than theMain Pad Keel, projects downwards from the Main Pad Keel on Second PadKeel Sides with Deadrise between 45 and 90 degrees. The Second Pad Keelis narrower and on the same longitudinal centerline as the Main Pad Keeland extends the full or optionally only a partial length of the Main PadKeel. The average Width measured at the Transom of the Main Pad Keel andSecond Pad Keel for a watercraft with a Length to Beam Ratio of lessthan three (3) is 10% to 20% of the Hall's Chine Beam measured at itsTransom. The average Width measured at the Transom of the Main Pad Keeland Second Pad Keel for a watercraft with a Length to Beam Ratio ofbetween three (3) and four (4) is 15% to 25% of the Hull's Chine Beammeasured at its Transom. The average Width measured at the Transom ofthe Main Pad Keel and Second Pad Keel for a watercraft with a Length ToBeam Ratio of four (4) or greater is 20% to 30% of the Hull's Chine Beammeasured at its Transom. In alternative embodiments, the width, heightor length of the Main Pad Keel or Second Pad Keel can be modifiedthrough mechanical actuation.

Shown in FIG. 1A is a Transom view 100 of a typical Deep-V watercraftwith an exploded view of a Main Pad Keel and Second Pad Keel Assembly102 that is detached from the Hull 104 in FIG. 1A and is shown attachedto the bottom of the Hull 106 in FIGS. 1B to 1H and 1J. FIG. 1B is abottom view 108 of this watercraft and FIG. 1C is a side view 110 ofthis watercraft. FIGS. 1D through 1H are section views of thiswatercraft from the Forefoot 112 to the Transom 114 whereby the Main PadKeel 116 projects downward from the bottom of the Hull 104 on Main PadKeel Sides 118 of 49 degrees. A Second Pad Keel 120 projects downwardfrom the Main Pad Keel 116 from Second Pad Keel Sides 122 of 90 degrees.FIG. 1J shows an isometric (aka perspective) view 124 of thiswatercraft. The Main Pad Keel 126 and Second Pad Keel 128 extendlongitudinally from their apex at the Bow 130 all the way to the Transom132. The Main Pad Keel 126 and Second Pad Keel 128 are widest at theTransom 132 and Taper in width towards the Bow 130. The watercraft inFIGS. 1A to 1H and 1J has a Design Waterline Length of 18.4′ and aDesign Waterline Beam of 7′. Its Length to Beam Ratio is 2.62 and theaverage width of the Main Pad Keel 126 and Second Pad Keel 128 at theTransom 132 is approximately 15% of its Hull Chine Beam 134 at theTransom 132.

When the Hull 106 of the watercraft shown in FIGS. 1A to 1H and 1Jreenters the water after becoming partially or fully airborne from thewater's surface, the Second Pad Keel 128 is the first Hull structure tomake contact. The dimensions of the Second Pad Keel 128 are selectedsuch that its impact generates an Acceptable Slamming Force whenfalling. The Second Pad Keel 128 impact imparts downward momentum to thewater with a force perpendicular to its surface.

FIG. 2A shows the flow directions 202 of the displaced water 204resulting from a Pad Keel 206 entering the water surface with verticalvelocity “v” 208. In a watercraft equipped with a Second Pad Keel, shownin FIG. 2C, the watercraft experiences Watercraft Re-Entry InitialDeceleration from the large vertical momentum imparted by the Second PadKeel 206 to the water 210 under it. Compare this to the waterdisplacement 212 in FIG. 2B as the result of a V-shaped structure 214entering the water surface 216 with vertical velocity 218. The impactforces act normal to its immersed bull panels 220 resulting in lowervertical momentum imparted to the water 222 as a result of the Deadrise224 of a watercraft equipped with hull panels having Deadrise 224 inFIG. 28 and therefore lower Watercraft Re-Entry Vertical Decelerationcompared to the Pad Keel 206 in FIG. 2A.

As shown in FIG. 2C, upon Re-entry of a watercraft equipped with a MainPad Keel and a Second Pad Keel, the Main Pad Keel 226 impacts the watersurface 228 shortly after the Second Pad Keel 230 and at a lowervelocity than the Second Pad Keel 230 as a result of the WatercraftReentry Initial Deceleration. The Main Pad Keel 226 impacts a DisturbedWater Surface 232 that has been displaced circumferentially by theimpact of the Second Pad Keel 230. Also, the water 234 below the MainPad Keel 226 and immediately adjacent to the Second Pad Keel Sides 236is accelerating downwardly as shown by the flow direction 238 in FIG.2C. The result of these factors is to reduce the force of a Slam of theMain Pad Keel 226 compared to if it had landed on an Undisturbed WaterSurface without a Second Pad Keel 230 landing immediately before it. TheSecond Pad Keel arrangement 240 therefore allows a watercraft having awider Main Pad Keel 226 to have a Slam force that is comparable to anarrower Pad Keel 206 without a Second Pad Keel arrangement 240.

In reference to FIG. 2C as a watercraft equipped with a Main Pad Keeland Second Pad Keel continues its downward Reentry, it experiencesadditional high Water Entry Deceleration from the large verticalmomentum imparted to the water under the wider and larger immersed Areaof the Main Pad Keel 226. Next, the Main Pad Keel Sides 242 becomeimmersed. It is well known that Hull Panels with Ultra-high Deadrisewhen Re-entering the water surface 228 have relatively small changes inpressure measured normal to the immersed Hull Panel surfaces. As theimmersion of the Main Pad Keel Sides 242 progresses, it does notcontribute a significant amount to further Water Entry Deceleration;however, the large vertical momentum imparted to the water under theMain Pad Keel 226 and Second Pad Keel 230 continues.

When the Second Pad Keel 240 is fully immersed, the ongoing Water EntryDeceleration from the Second Pad Keel 240 has continued long enough thatthe watercraft vertical plunging velocity 244 has slowed. Therefore,when parts of the Hull above the Main Pad Keel Sides 242 impact thewater surface, the Slamming forces are Acceptable Slamming Forces.

FIGS. 3A to 3H and 3J show another embodiment of the invention. TheSecond Pad Keel 302 of the Concentric Pad Keel 304 terminates at Midship306, rather than extending longitudinally the full length of thewatercraft to the Transom 308.

FIG. 3A shows the Bow Pocket Vents 310 located on the forward end of theport and starboard Main Pad Keel Sides 312, aft of the Bow Stem 314.This opening has a Spray Deflector 316 “pocket” to allow atmospheric airto vent the Hollow Plenum 318, shown in FIGS. 3F-3H. On the forwardbottom of the Main Pad Keel 320 is an opening 322 to allow air to enter,or “vent”, the Second Pad Keel Plenum 324, shown in FIG. 3G, and shownin the exploded view with dashed lines in reference to Bow Pocket Vents310. The aft end of the Second Pad Keel Plenum 324 is open, allowing airto ventilate the Hull surfaces aft of the outlet to reduce WettedSurface Area and Viscous Drag at Planing speeds.

At zero and low speeds the Concentric Pad Keel Plenums 318, 324Self-Flood with water entering through the Plenum openings 322 below thewater surface and displace air in the Plenum which exits through the BowPocket Vent 310. Water in the Plenums lowers the vertical center ofgravity of the watercraft to reduce motions at zero and low speeds, toimprove Seakeeping, and to improve Seakindliness. When the watercraftaccelerates to Planing speeds, the BOW Pocket Vent 310 rises above thewater surface, and the intake air feeds into the Plenums 318, 324 of theConcentric Pad Keel, which Self-Bail through outlets 322 on theConcentric Pad Keel.

Cross-sections 326 of the Concentric Pad Keel 304, shown in FIGS. 3Dthrough 3H, show the Main Pad Keel Plenum 318 and the Second Pad KeelPlenum 324 terminating near mid-length 306 (shown in FIG. 3B) of theMain Pad Keel 320 and at the aft end of the Second Pad Keel 302 (shownin FIG. 3C).

FIG. 3J shows an exploded bottom isometric view 328 of the ConcentricPad Keel 304, and shows the Self-Flood and Self-Bail channel openings330 between the Main Pad Keel Plenum 318 and the Second Pad Keel Plenum324. Structurally, the Second Pad Keel 302 can be fastened to the MainPad Keel 320 as an add-on and can be fabricated from the same materialas the hull or a different material based on its intended use. Forexample, for grounding protection, the Second Pad Keel 302 can befabricated from a sacrificial material such as foam, plastic, aluminumor another known or convenient material.

FIGS. 4A-C depict a Uniform Second Pad Keel, which is anotherembodiment. As depicted in FIGS. 4A-C, the Second Pad Keel 402terminates at the Transom 404, extending longitudinally the full lengthof the watercraft from the Forward Apex 406 to the Transom 404. As shownin FIGS. 4A-C, the Second Pad Keel 402 is neither Expanding in the YDimension nor Rockered in the Z Dimension. In this example, the SecondPad Keel 402 Tapers in the Z Dimension in the Forward End from 1″ at theTransom 404 to ½″ at the Forward Apex 406. Other rates of Taper from theForward End can be used.

FIGS. 5A-C depict a Truncated, Ventilating Second Pad Keel. As depictedin FIGS. 5A-C, the Second Pad Keel 502 Truncates at a point Forward ofthe Transom 504. The purpose for this is to Ventilate the Main Pad Keel506 through openings in the Plenum 508. This configuration is neitherExpanding in the Y dimension nor Rockered in the Z dimension.

FIGS. 6A-C depict a Truncated, Aft Rockered Second Pad Keel. As depictedin FIGS. 6A-C, the Second Pad Keel 602 Rockers to a point forward of theTransom 604. The Height of the Second Pad Keel Sides 606 Tapers fromabout 1″ at the Keel to 0″-½″ at its Aft End. This configuration is notExpanding.

FIGS. 7A-C depict an Aft Expanding Second Pad Keel. This is anembodiment where the Second Pad Keel 702 Tapers Outboard so that theSecond Pad Keel Sides 704 blend with the Main Pad Keel Sides 706. TheDeadrise on the Second Pad Keel Sides 704 varies from 90° at the ForwardEnd of the Taper to a Deadrise equal to the Main Pad Keel Sides 706 atthe Aft End of the Taper. As depicted, this Taper in Width constitutesvariability in the Y dimension.

FIGS. 8A-C depict an Aft Expanding and Rockered Second Pad Keel. Asdepicted in FIGS. 8A-C, the Second Pad Keel 802 Tapers Outboard so thatthe Second Pad Keel Sides 804 blend with the Main Pad Keel Sides 806.The Deadrise on the Second Pad Keel Sides 804 varies from 90° at theForward End of the Taper to a Deadrise matching the Main Pad Keel Sides806 at the Aft End of the Taper. Additionally, the Second Pad Keel 802Rockers towards its Aft End 808. The height of the Second Pad Keel Sides804 Tapers from about 1″ at the keel to 0″-½″ at its Aft End 808.

FIGS. 9A-C depict an Aft End Rocketed Second Pad Keel. As depicted inFIGS. 9A-C, the Second Pad Keel 902 Rockers to the Transom 904. TheHeight of the Second Pad Keel Sides 906 Tapers front about 1″ at theKeel to 0″-½″ at the Transom 904. As depicted, this Taper in Heightconstitutes variability in the Z dimension.

FIGS. 10A-C depict an Aft Expanding, Truncated and Ventilating SecondPad Keel. As depicted in FIG. 10A-C, the Second Pad Keel 1002 TapersOutboard so that the Second Pad Keel Sides 1004, which have constantDeadrise of 90° at the Forward Apex 1006, blend with the Main Pad KeelSides 1008 at a point forward of the Transom 1010.

FIGS. 11A-C depict an Aft Expanding, Truncated and Rockered Second PadKeel. As depicted in FIGS. 11A-C, the Second Pad Keel 1102 TapersOutboard so that the Second Pad Keel Sides 1104, having constantDeadrise of 90° at the Forward Apex 1106, blend with the Main Pad KeelSides 1108 at a point forward of the Transom 1110. Additionally, theSecond Pad Keel 1102 Rockers to a point forward of the Transom 1110,where it is Truncated. The Height of the Second Pad Keel Sides 1104Tapers from about 1″ at the Keel to 0″-½″ at the Aft End of thewatercraft.

It will be appreciated to those skilled in the art that the precedingexamples and embodiments are exemplary and not limiting to the scope ofthe present invention. It is intended that all permutations,enhancements, equivalents, and improvements thereto that are apparent tothose skilled in the art upon a reading of the specification and a studyof the drawings are included within the true spirit and scope of thepresent invention. It is therefore intended that the following appendedclaims include all such modifications, permutations and equivalents asfall within the true spirit and scope of the present invention.

What is claimed:
 1. A watercraft including a Deep-V Planing Hullcomprising: a Fine Entry Bow: a Transom; and a Variable Second Pad Keelhaving, a Main Pad Keel projecting downward from the Deep-V Planing Hullon Ultra High Deadrise Main Pad Keel Sides, and a Second Pad Keelprojecting downward from the Main Pad Keel on Ultra High Deadrise SecondPad Keel Sides; wherein the Second Pad Keel Sides Taper from the Transomto an apex at the Forefoot of the Fine Entry Bow.
 2. The watercraft ofclaim 1, wherein the Second Pad Keel is Uniform.
 3. The watercraft ofclaim 1, wherein the Second Pad Keel is Truncated forward of theTransom; and wherein the Plenum in the Second Pad Keel is ventilated,thereby ventilating the Main Pad Keel.
 4. The watercraft of claim 1,wherein the Second Pad Keel is Rocketed.
 5. The watercraft of claim 4,wherein the Second Pad Keel is Rocketed from a Height of 1 inch at theForward End to a Height in a range of 0 inches to ½ inches as die AftEnd.
 6. The watercraft of claim 1, wherein the Second Pad Keel Expandsin Width to Blend with the Main Pad Keel Sides; wherein the Second PadKeel Sides Deadrise varies from 90 degrees at a Forward End of theSecond Pad Keel to Blend to the Deadrise of the Main Pad Keel Sides atthe Aft End of the Second Pad Keel.
 7. The watercraft of claim 1,wherein the Second Pad Keel Expands in Width to Blend with the Main Padkeel Sides; wherein the Second Pad keel Sides Deadrise varies from 90degrees at a Forward End of the Second Pad Keel to Blend to the Deadriseof the Main Pad Keel Sides at the Aft End of the Second Pad Keel; andwherein the Second Pad Keel is Rockered.
 8. The watercraft of claim 7,wherein the Second Pad Keel is Rockered from a height of 1 inch to aheight in a range of 0 inches to ½ inches.
 9. The watercraft of claim 1,wherein the Second Pad Keel is Rockered to the Transom.
 10. Thewatercraft of claim 6, wherein the Second Pad Keel is Rockered from aheight of 1 inch to a height in a range of 0 inches to ½ inches.
 11. Thewatercraft of claim 1, wherein the Second Pad Keel Expands with theSecond Pad Keel Sides having a constant deadrise of 90 degrees; andwherein the Second Pad Keel Sides Blend with the Main Pad Keel Sides ata point forward of the Transom.
 12. The watercraft of claim 1, whereinthe Second Pad Keel Expands with Second Pad Keel Sides having a constantDeadrise of 90 degrees; wherein the Second Pad Keel Sides Blend with theMain Pad Keel Sides at a point forward of the Transom; wherein theSecond Pad Keel is Truncated and Rockers to a point forward of theTransom; and wherein the Second Pad Keel Sides Taper.
 13. The watercraftof claim 1, wherein the Second Pad Keel Sides Tapers from a Height of 1inch to a Height in a range of 0 inches to ½ inches.
 14. The watercraftof claim 1, wherein the watercraft has a Waterline Length To Beam Ratioof less than 3 and an average Width measured at the Transom of the MainPad Keel and the Second Pad Keel is between 10 percent to 20 percent ofa Hull Chine Beam measured at the Transom.
 15. The watercraft of claim1, wherein the watercraft has a Waterline Length To Beam Ratio ofbetween 3 and 4 and an average Width measured at the Transom of the MainPad Keel and the Second Pad Keel is between 15 percent to 25 percent ofa Hull Chine Beam measured at the Transom
 16. The watercraft of claim 1,wherein the watercraft has a Waterline Length To Beam Ratio of 4 orgreater and an average Width measured at the Transom of the Main PadKeel and the Second Pad Keel is between 20 percent to 30 percent of aHull Chine Beam measured at the Transom.